A photographic plate-making process, in which a silver halide photographic light-sensitive material is used, include, for example, a step for converting a continuous-tone original into a halftone dot image, that is, a step for converting a continuous gradation density variation into an aggregate of halftone dots having an area proportionate to the density, and another step for converting the halftone dot image obtained in the above-mentioned step into a halftone dot image having more excellent sharpness, that is, a contact step.
It is inevitable that the light-sensitive material applicable to these steps is to have a high contrast, because an excellent halftone dot quality is required.
As for the processes for obtaining the above-mentioned characteristics, there has been a well-known process in which a light-sensitive material comprising a silver chlorobromide emulsion having relatively fine grains, a narrow grain-size distribution and a high silver chloride content, such light-sensitive material is processed by an alkaline hydroquinone developer having an extremely low sulfurous acid ion concentration, that is so-called a lith development process.
When the process is used, however, there has raised such a defect that a preservability is seriously deteriorated, because a sulfurous acid ion concentration has been low in a developer and a development speed has been slowed down, because a single hydroquinone developing agent is used, so that a rapid processing has not been achieved.
Accordingly, there has been a demand for the development of a novel light-sensitive material capable of providing a high contrast when processing it with a so-called PQ or MQ type developer, which contains a developing agent having an excellent preservability, a rapid processability and a super additive property and a sulfurous acid salt having a relatively high concentration. As for the novel light-sensitive materials, the silver halide photographic light-sensitive materials each containing a tetrazolium compound are disclosed in, for example, Japanese Patent Publication Nos. 59-17825/1984, 59-17818/1984, 59-17819/1984, 59-17820/1984, 59-17821/1984, 59-17826/1984 and 59-17822/1984.
On the other hand, the processes for rapidly obtaining a high contrast image based on the other principles are disclosed as cited in, for example, U.S. Pat. Nos. 2,419,975 and 4,224,401 and Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP OPI Publication) Nos. 51-16623/1976 and 51-20921/1976; and the silver halide photographic light-sensitive materials each containing a hydrazine compound are disclosed as cited in, for example, U.S. Pat. Nos. 2,419,975 and 4,224,401 and JP OPI Publication Nos. 51-16623/1976 and 51-20921/1976.
On the other hand, however, such a hard contrast light-sensitive material as mentioned above has a defect that a letter reproducibility is deteriorated when a line image is photographed. To be more concrete, in the case where, for example, an original with a mixture of 7-point Ming type and Gothic types is exposed to light through a photographic process camera and when the fine line of the Ming type is exposed to light so as not to be defaced, the background density which should be defaced in black is lowered to increase pin-holes and the line width of Gothic type is made fine without thickening to a desired Gothic type thickness. On the contrary, when an exposure quantity is adjusted to meet the line width of Gothic type, the fine line of Ming type is defaced. In the printing and print-making industry, therefore, there uses such a process that Ming type and Gothic type are separately photographed and then to synthesize the two in the post processing step. In this process, however, the labor and material are required double or more.
Also in an operation for enlarging or reducing an original converted into halftone dots, that is so-called a screen-image enlarging, there is a problem that a halftone dot range is clogged when a hard contrast light-sensitive material is used. Therefore, for a screen-image enlarging, an exposure is usually made through a so-called Lee filter. However, there also raises a problem, because a filter has to be attached and detached every time when making an exposure and a finished quality is varied by the deterioration of the filter used.
Recently, a silver halide photographic light-sensitive material so stable and operationally efficient as to be handled by any amateur has been demanded, due to the shortage of labor force especially including skilled workers and the increase of unskilled workers.
As described in JP OPI Publication No. 3-290644/1991, there has been an increasing necessity for a silver halide photographic light-sensitive material better in the enlargement or reduction of a screen-image and in Ming type-Gothic type reproduction aptitude and further better in white-on-color letter quality, paste-up trace prevention and, besides, pin-hole prevention.